Question

PLEASE HELP!!!!!! 20 POINTS!!!!!

Answer 1

-18.703

Explanation:

a₁=-28(-1/2)¹⁻¹

r=-1/2

a₁=-28

r=-1/2

S₉=a₁
`(1-r^(9) )/(1-r)`

S₉=-28
`(1-((1)/(2))^(9) )/(1-((1)/(2)) )`

S₉=
`-(1197)/(64)`

S₉=-18
`(45)/(64)` S₉=-18.703125